Can we please stop talking about the presidential debates as though they are used rationally by voters as they make up their minds about the election?
Most people—the vast majority of people—have already made up their minds. That goes for the so-called "undecideds" as well, since most of them aren't really undecided. They just like keeping their options open, kind of like Goldie Hawn and Kurt Russell (well, before they broke up). Even independents aren't all that independent, pollsters have found. Most of them identify with one or the other party despite the "independent" moniker. I have no problem with this. I myself once tried to register as a "Druid" here in D.C., really just to be difficult and because I was curious about what they'd do. (They put me down as "unaffiliated.") For most voters, the debates serve mainly to reinforce the choices they've already made.
What about the winner of the debate? There is none, and it doesn't matter anyway. This is not a test of debate skills (an issue made even more hilarious by both sides tamping down expectations, saying their guy is really not such a good debater and the other one is better than everyone thinks). Someone "wins" a point when someone says something a voter likes. Anyway, when did the best debater ever really win? It's like high school, when the chairman of the debate team runs for class president, and is beaten by the football player (and the girl gets to be vice president and do all the work). Everyone claims to want a smart president, but nobody wants a smarty-pants. That's part of the reason Al Gore suffered in his debate against George W. Bush—knowing more wasn't an asset.
The real reason we watch debates is similar to why many of us watch figure skating competitions. Sure, it's great to see the spectacular jump or graceful glide. But we're also sitting somewhat anxiously, wondering if the skater will stumble and fall onto the ice. It would take a big fall by either candidate in this debate to make a difference. And even then, the stumbler's supporters might see it as a media conspiracy to damage their candidate. Debates should be substantive and meaningful. But for much of the electorate, they're just a somewhat more sophisticated element of reality TV.